Date: Thu, 1 Apr 2021 08:03:57 GMT From: Richard Scheffenegger <rscheff@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 529a2a0f2765 - main - tcp: For hostcache performance, use atomics instead of counters Message-ID: <202104010803.13183vQe043756@gitrepo.freebsd.org>
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The branch main has been updated by rscheff: URL: https://cgit.FreeBSD.org/src/commit/?id=529a2a0f2765f6c57c50a5af6be242c03bf714e3 commit 529a2a0f2765f6c57c50a5af6be242c03bf714e3 Author: Richard Scheffenegger <rscheff@FreeBSD.org> AuthorDate: 2021-04-01 08:00:32 +0000 Commit: Richard Scheffenegger <rscheff@FreeBSD.org> CommitDate: 2021-04-01 08:03:30 +0000 tcp: For hostcache performance, use atomics instead of counters As accessing the tcp hostcache happens frequently on some classes of servers, it was recommended to use atomic_add/subtract rather than (per-CPU distributed) counters, which have to be summed up at high cost to cache efficiency. PR: 254333 MFC after: 2 weeks Sponsored by: NetApp, Inc. Reviewed By: #transport, tuexen, jtl Differential Revision: https://reviews.freebsd.org/D29522 --- sys/netinet/tcp_hostcache.c | 24 +++++++++++------------- sys/netinet/tcp_hostcache.h | 2 +- 2 files changed, 12 insertions(+), 14 deletions(-) diff --git a/sys/netinet/tcp_hostcache.c b/sys/netinet/tcp_hostcache.c index 67da97405c3f..87023cc1a760 100644 --- a/sys/netinet/tcp_hostcache.c +++ b/sys/netinet/tcp_hostcache.c @@ -147,8 +147,8 @@ SYSCTL_UINT(_net_inet_tcp_hostcache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN, &VNET_NAME(tcp_hostcache.bucket_limit), 0, "Per-bucket hash limit for hostcache"); -SYSCTL_COUNTER_U64(_net_inet_tcp_hostcache, OID_AUTO, count, CTLFLAG_VNET | CTLFLAG_RD, - &VNET_NAME(tcp_hostcache.cache_count), +SYSCTL_UINT(_net_inet_tcp_hostcache, OID_AUTO, count, CTLFLAG_VNET | CTLFLAG_RD, + &VNET_NAME(tcp_hostcache.cache_count), 0, "Current number of entries in hostcache"); SYSCTL_INT(_net_inet_tcp_hostcache, OID_AUTO, expire, CTLFLAG_VNET | CTLFLAG_RW, @@ -199,8 +199,7 @@ tcp_hc_init(void) /* * Initialize hostcache structures. */ - V_tcp_hostcache.cache_count = counter_u64_alloc(M_WAITOK); - counter_u64_zero(V_tcp_hostcache.cache_count); + atomic_store_int(&V_tcp_hostcache.cache_count, 0); V_tcp_hostcache.hashsize = TCP_HOSTCACHE_HASHSIZE; V_tcp_hostcache.bucket_limit = TCP_HOSTCACHE_BUCKETLIMIT; V_tcp_hostcache.expire = TCP_HOSTCACHE_EXPIRE; @@ -268,9 +267,6 @@ tcp_hc_destroy(void) /* Purge all hc entries. */ tcp_hc_purge_internal(1); - /* Release the counter */ - counter_u64_free(V_tcp_hostcache.cache_count); - /* Free the uma zone and the allocated hash table. */ uma_zdestroy(V_tcp_hostcache.zone); @@ -378,7 +374,7 @@ tcp_hc_insert(struct in_conninfo *inc) * If the bucket limit is reached, reuse the least-used element. */ if (hc_head->hch_length >= V_tcp_hostcache.bucket_limit || - counter_u64_fetch(V_tcp_hostcache.cache_count) >= V_tcp_hostcache.cache_limit) { + atomic_load_int(&V_tcp_hostcache.cache_count) >= V_tcp_hostcache.cache_limit) { hc_entry = TAILQ_LAST(&hc_head->hch_bucket, hc_qhead); /* * At first we were dropping the last element, just to @@ -395,7 +391,7 @@ tcp_hc_insert(struct in_conninfo *inc) } TAILQ_REMOVE(&hc_head->hch_bucket, hc_entry, rmx_q); V_tcp_hostcache.hashbase[hash].hch_length--; - counter_u64_add(V_tcp_hostcache.cache_count, -1); + atomic_subtract_int(&V_tcp_hostcache.cache_count, 1); TCPSTAT_INC(tcps_hc_bucketoverflow); #if 0 uma_zfree(V_tcp_hostcache.zone, hc_entry); @@ -428,7 +424,7 @@ tcp_hc_insert(struct in_conninfo *inc) */ TAILQ_INSERT_HEAD(&hc_head->hch_bucket, hc_entry, rmx_q); V_tcp_hostcache.hashbase[hash].hch_length++; - counter_u64_add(V_tcp_hostcache.cache_count, 1); + atomic_add_int(&V_tcp_hostcache.cache_count, 1); TCPSTAT_INC(tcps_hc_added); return hc_entry; @@ -644,7 +640,8 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS) /* Optimize Buffer length query by sbin/sysctl */ if (req->oldptr == NULL) { - len = (counter_u64_fetch(V_tcp_hostcache.cache_count) + 1) * linesize; + len = (atomic_load_int(&V_tcp_hostcache.cache_count) + 1) * + linesize; return (SYSCTL_OUT(req, NULL, len)); } @@ -654,7 +651,8 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS) } /* Use a buffer sized for one full bucket */ - sbuf_new_for_sysctl(&sb, NULL, V_tcp_hostcache.bucket_limit * linesize, req); + sbuf_new_for_sysctl(&sb, NULL, V_tcp_hostcache.bucket_limit * + linesize, req); sbuf_printf(&sb, "\nIP address MTU SSTRESH RTT RTTVAR " @@ -716,7 +714,7 @@ tcp_hc_purge_internal(int all) hc_entry, rmx_q); uma_zfree(V_tcp_hostcache.zone, hc_entry); V_tcp_hostcache.hashbase[i].hch_length--; - counter_u64_add(V_tcp_hostcache.cache_count, -1); + atomic_subtract_int(&V_tcp_hostcache.cache_count, 1); } else hc_entry->rmx_expire -= V_tcp_hostcache.prune; } diff --git a/sys/netinet/tcp_hostcache.h b/sys/netinet/tcp_hostcache.h index b5237392acc2..2f7035c0c6af 100644 --- a/sys/netinet/tcp_hostcache.h +++ b/sys/netinet/tcp_hostcache.h @@ -74,7 +74,7 @@ struct tcp_hostcache { u_int hashsize; u_int hashmask; u_int bucket_limit; - counter_u64_t cache_count; + u_int cache_count; u_int cache_limit; int expire; int prune;
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